Assertion `(A)`: Hydrogen oxidises lithium to `Li`.
Reason `(R)` : Hydrogen cannot act as oxidising agent.

Options

A. If both (A) and (R) are correct and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect, but (R) is correct.

Explanation

To analyze the given assertion and reason, we will break it down into steps:

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Hydrogen oxidizes lithium to Li⁺."
- Oxidation refers to the loss of electrons. When lithium (Li) is oxidized, it loses an electron to form Li⁺.

2. **Understanding the Reason (R)**:
- The reason states that "Hydrogen cannot act as an oxidizing agent."
- An oxidizing agent is a substance that gains electrons in a chemical reaction and, in the process, causes another substance to be oxidized.

3. **Analyzing the Role of Hydrogen**:
- Hydrogen can act as both an oxidizing agent and a reducing agent, depending on the reaction context.
- When hydrogen reacts with metals, it can gain electrons and thus act as an oxidizing agent. This means it can oxidize metals like lithium.

4. **Evaluating the Assertion**:
- Since hydrogen can oxidize lithium to Li⁺, the assertion is **true**.
- The reaction can be represented as:
\[ 2Li + H_2 \rightarrow 2LiH \]
- In this reaction, lithium (Li) is oxidized from an oxidation state of 0 to +1.

5. **Evaluating the Reason**:
- The reason that "Hydrogen cannot act as an oxidizing agent" is **false** because hydrogen does indeed act as an oxidizing agent when it reacts with metals.

6. **Conclusion**:
- The assertion is true, while the reason is false. Therefore, the correct conclusion is that the assertion is correct, but the reason is not.

### Final Answer:
- Assertion (A) is true, and Reason (R) is false.